1. Field of the Invention
The present invention relates to a telephone having a display.
2. Description of the Related Art
A communication device such as a telephone or the like frequently has a display. However, the display is operated even when the user has no need to see the display, and thus electric power is uselessly consumed.
Considering this problem, a telephone has been proposed in which a back light of a display indicating a calling dial number and so on is turned off if no key input is performed for a predetermined time.
In this telephone, as shown in FIG. 9, it is checked whether or not by the ten key pad or a function key are operated, and whether or not the hook state is changed, i.e., whether or not the on-hook state is changed to the off-hook state, or vice versa (Steps S41 and 42). At this time the backlight LED (Light Emitting Diode) is turned off. This check is continued until key input is performed, or the hook state is changed. If key input is performed, or if the hook state is changed, the LED is lighted (Step S43). At the time of a call, the flow also goes to Step S43.
A timer then starts to count (Step S44). A check is then made as to whether or not the hook state is changed (Step S45) and whether or not key input is performed (Step S46). When either a change in the hook state or key input is detected, the timer is initialized (Step S44). A check is made again as to whether or not the hook state is changed (Step S45) or whether or not key input is performed (Step S46), and the above operation is repeated. When the hook state is not changed (S45) or key input is not performed (S46) for a predetermined time, the timer assumes the time-out state (Step S47), and the back light LED is turned off (Step S48). The flow then returns to the initial state (Step S40), and the above operation is repeated.
However, when the back light LED is to be turned off at the time the count value of the timer reaches a predetermined value, as described above, it is difficult to set an appropriate value for the timer because of differences in preferred values among operators.
In addition, since the display time depends upon the display contents, it is sometimes unsuitable to turn off the back light LED in the time-out state of the timer.